Higher order diffractions from a circular disk

The backscattering from a circular disk is analyzed using the geometrical theory of diffraction (GTD). First-, second-, and third-order diffractions are included in the hard polarization analysis, while first-, second-, and second-order slope diffractions are included for soft polarization. Improvements in the prediction of the monostatic radar cross section (RCS) over previous works are noted. For hard polarization, an excellent agreement is exhibited between experimental and theoretical results, while a very good agreement is noted for soft polarization. To further improve the soft polarization results for wide angles, a model for the creeping wave or circulating current on the edge of the disk is obtained and used to find an additional component of the backscattered field. The addition of this component significantly improves the results for wide angles, leading to excellent agreement for soft polarization also. An axial-caustic correction method using equivalent currents is also included in the analysis.